The operating frequencies of a variety of electronic equipment have increased in recent years, and with such an increase in operating frequencies, there is also a need for piezoelectric resonator devices (crystal resonators, for example) to take measures against such an increase in operating frequencies.
Many of such kinds of piezoelectric resonator devices have a casing in the form of a rectangular parallelepiped package. Such a package is configured with first and second sealing members of glass and a crystal resonator plate of quartz that has driving electrodes formed on both major surfaces. The first sealing member and the second sealing member are laminated and bonded together via the crystal resonator plate so as to hermetically seal the driving electrodes of the crystal resonator plate provided inside the package (see Patent Document 1 below, for example).